Tuesday, May 14, 2019

Release early and often

release-frequently

This post summarizes the virtues of cutting frequent releases for software projects. You might find this post useful if you are trying to convince others to release more frequently (such as your company or an open source project you contribute to).

Easing migration

Frequent releases provide a smoother migration path for end-users of your software.

For example, suppose that your software is currently version “1.0” and you have two breaking changes (“A” and “B”) that you plan to make. Now consider the following two release strategies

  • Release strategy #0 - More frequent releases

    * Version 1.0
        * Initial release
    
    * Version 2.0
        * BREAKING CHANGE: A
    
    * Version 3.0
        * BREAKING CHANGE: B
  • Release strategy #1 - Less frequent releases

    * Version 1.0
        * Initial release
    
    * Version 2.0
        * BREAKING CHANGE: A
        * BREAKING CHANGE: B

The first release strategy is better from the end-user’s point of view because they have the option to upgrade in two smaller steps. In other words, they can upgrade from version 1.0 to version 2.0 and then upgrade from version 2.0 to version 3.0 at a later date.

Under both release strategies users can elect to skip straight to the latest release if they are willing to pay down the full upgrade cost up front, but releasing more frequently provides users the option to pay down the upgrade cost in smaller installments. To make an analogy: walking up a staircase is easier than scaling a sheer cliff of the same height.

In particular, you want to avoid the catastrophic scenario where a large number of users refuse to upgrade if one release bundles too many breaking changes. The textbook example of this is the Python 2 to 3 upgrade where a large fraction of the community refused to upgrade because too many breaking changes were bundled into a single release instead of spread out over several releases.

Keeping trains running on time

You don’t need to delay a release to wait for a particular feature if you release frequently. Just postpone the change for the next release if it’s not ready. After all, if you release frequently then the next release is right around the corner.

Conversely, if you release infrequently, you will frequently run into the following vicious cycle:

  • Important feature X is close to completion but perhaps not quite ready to merge

    Perhaps the feature has insufficient tests or there are unresolved concerns during code review

  • A new release is about to be cut

    Should you wait to merge feature X? It might be a long time (3 months?) before the next release, even though X could be ready with just 1 more week of work.

  • You choose to delay the release to wait for important feature X

  • Now another important feature Y requests to also slip in before the release

    … further delaying the release

  • 3 months have passed and you still haven’t cut the release

    New features keep (justifiably) slipping in out of fear that they will have to otherwise wait for the next release

Eventually you do cut a release, but each iteration of this process decreases the release frequency and compounds the problem. The less frequently you release software the more incentive to slip in last-minute changes before the release cutoff, further delaying the release. Even worse, the longer you wait to cut each release the greater the pressure to compromise on quality to get the release out the door.

Sticking to a strict and frequent release schedule staves off this vicious cycle because then you can always safely postpone incomplete features to the next release.

Avoiding “crunch time”

Infrequent “big bang” releases create pressure for developers to work excessive hours in the lead up to a release cutoff. This can happen even when developers are unpaid, such as on open source projects: the peer pressure of holding up the release for others can induce people to work unhealthy schedules they wouldn’t work otherwise.

I won’t claim that frequent release schedules will prevent paid developers from working late nights and weekends, but at least management can’t hide behind a looming release deadline to justify the overtime.

Accelerating the feedback loop

Releases are opportunities to correct course because you don’t know how users will react to a feature until you put the feature into their hands. If you implement a feature and the next release is 3 month away, that’s 3 months where you don’t know if the feature is what the user actually needs.

Even worse: suppose that the first implementation of the feature does not do what the user wants: now you have to wait another 3 months to get the next iteration of the feature into their hands. That slow feedback loop is a recipe for a poorly-designed product.

Incentivizing automation

Fast release cycles force you to automate and accelerate release-related processes that you would otherwise do manually (i.e. continuous integration), including:

  • Testing
  • Publication of software artifacts
  • Collecting quality and health metrics

That automation in turn means that you spend more time in the long run developing features and less time delivering them to end users.

Conclusion

Releasing more frequently isn’t free: as the previous section suggests, you need to invest in automation to be able to make frequent releases a reality.

However, I do hope that people reading this post will recognize when symptoms of infrequent releases creep up on them so that they can get ahead of them and make the case to others to invest in improving release frequency.